Jerusalem  - Israeli caretaker Prime Minister Ehud Olmert warned Israel would respond to a surge in rocket attacks from the Gaza Strip Wednesday.

"It is clear that this fire only sharpens what we have said all the time. There cannot be a situation in which it has been agreed that there is calm (a truce), but at the same time the reality on the ground is complete different," he told reporters as he cast his vote in a primary of his ruling Kadima party.

"Of course this requires us to relate to it and will relate to it," he said.

Palestinian militants intensified their rocket attacks from Gaza Wednesday, as an Egyptian-brokered six-month informal truce between Israel and Palestinian armed factions in the strip is due to expire early Friday.

Some 20 rockets and one mortar shell were launched at southern Israel by late Wednesday evening, a military spokeswoman in Tel Aviv said.

One of them landed just outside a shopping centre in the southern Israeli town of Sderot, lightly injuring three Israelis.

Despite the warnings, senior Israeli defence officials told Israel's Channel 1 television they believe "this is not the time for a broad (military) operation in Gaza," while also Channel 10 television reported that the Israeli military and defence ministry were "very uneager to return to Gaza" three years after Israel unilaterally withdrew from the strip in 2005.

Israeli Defence Minister Ehud Barak reiterated Wednesday evening that Israel does "not shrink from a broad action in Gaza, but we are also not running toward such an action. When the situation obliges us to act, we will act." (dpa)